100+ Free ABC Wastewater Treatment Class II Practice Questions
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Approximately how many mg of alkalinity (as CaCO3) are consumed per mg of ammonia-nitrogen oxidized during nitrification?
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Key Facts: ABC Wastewater Treatment Class II Exam
100
Scored Questions
WPI Class II exam outline
+10
Possible Unscored Pretest
WPI need-to-know criteria
3 hours
Time Limit
WPI-style exam policy
70%
Passing Score
WPI-style exam policy
Class II
Small-to-Medium Facility Tier
ABC/WPI certification structure
$69+
WPI Exam Sitting Fee
WPI / PSI exam process
The ABC/WPI Wastewater Treatment Operator Class II exam uses the 2025 standardized blueprint with 100 scored multiple-choice questions, up to 10 unscored pretest items, a 3-hour time limit, and a 70% passing score. Class II covers all Class I fundamentals plus deeper activated sludge process control (SRT, F/M, SVI), biological nutrient removal (nitrification, denitrification, EBPR), tertiary filtration, anaerobic and aerobic digestion, 40 CFR Part 503 biosolids handling, and Class II safety responsibilities. Approximately 14% of questions involve calculations. Class II typically authorizes operation of small-to-medium facilities, with thresholds set by each state.
Sample ABC Wastewater Treatment Class II Practice Questions
Try these sample questions to test your ABC Wastewater Treatment Class II exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.
1Which formula correctly calculates Solids Retention Time (SRT) for an activated sludge plant?
2A Class II plant targets full nitrification at 20 degrees C. Which SRT range is generally appropriate?
3An operator wants to lengthen SRT. What is the correct action?
4What does the F/M ratio compare?
5As SRT increases, what generally happens to the F/M ratio at constant influent loading?
6What does Sludge Volume Index (SVI) measure?
7MLSS is 2,500 mg/L and the 30-minute settled volume is 250 mL/L. What is the SVI?
8What is the difference between MLSS and MLVSS?
9Pin floc and a turbid effluent often indicate which sludge condition?
10Dispersed growth and cloudy effluent at very young sludge age most likely means:
About the ABC Wastewater Treatment Class II Exam
Class II practice exam for the ABC/WPI standardized wastewater treatment operator certification used by most state programs. Class II authorizes operation of small-to-medium facilities and adds biological nutrient removal and advanced process control to the Class I foundation.
Assessment
100 scored multiple-choice questions plus up to 10 unscored pretest questions
Time Limit
180 minutes
Passing Score
70%
Exam Fee
Approximately $69 WPI exam sitting fee plus state application fees (Association of Boards of Certification (ABC) / Water Professionals International (WPI))
ABC Wastewater Treatment Class II Exam Content Outline
Treatment Process Evaluation and Adjustment
Activated sludge process control using SRT, F/M, SVI, and settleability; nitrification and denitrification; biological and chemical phosphorus removal; filamentous bulking; selectors; tertiary filtration; and effluent disinfection.
Equipment Operation and Maintenance
Headworks screens and grit, RAS and WAS pumps, blowers and diffusers, clarifier mechanisms, tertiary filters, UV and chlorine systems, anaerobic and aerobic digesters, thickening and dewatering, and SCADA instrumentation.
Laboratory Analysis
Sampling and preservation, QA/QC, BOD, TSS, MLSS, MLVSS, SVI, DO, alkalinity, ammonia, nitrite, nitrate, phosphorus, chlorine residual, and wastewater math for loading and dosage.
Safety, Security, and Administrative Procedures
Confined space entry, digester methane and H2S hazards, chemical safety, NPDES permit compliance, 503 biosolids recordkeeping, emergency response, and facility security.
How to Pass the ABC Wastewater Treatment Class II Exam
What You Need to Know
- Passing score: 70%
- Assessment: 100 scored multiple-choice questions plus up to 10 unscored pretest questions
- Time limit: 180 minutes
- Exam fee: Approximately $69 WPI exam sitting fee plus state application fees
Keys to Passing
- Complete 500+ practice questions
- Score 80%+ consistently before scheduling
- Focus on highest-weighted sections
- Use our AI tutor for tough concepts
ABC Wastewater Treatment Class II Study Tips from Top Performers
Frequently Asked Questions
What is the ABC Wastewater Treatment Operator Class II exam?
Class II is the second tier of the ABC/WPI standardized wastewater treatment operator certification used by most state authorities. It authorizes operation of small-to-medium facilities and adds biological nutrient removal, anaerobic digestion, and advanced process control to the Class I foundation.
How many questions are on the Class II exam?
The Class II exam includes 100 scored multiple-choice questions and may include up to 10 unscored pretest items. Jurisdictions using the WPI format allow 3 hours and require a 70% passing score on the 100 scored questions.
How does Class II differ from Class I?
Class II covers every Class I topic plus deeper activated sludge process control such as setting SRT and F/M, calculating SVI, nitrification and denitrification, EBPR, anaerobic digestion, tertiary filtration, 40 CFR Part 503 biosolids requirements, and digester safety. Class I focuses more on fundamentals and recall.
Is Class I required before Class II?
Most states require operators to hold Class I certification, plus documented operating experience, before sitting for Class II. Some jurisdictions allow direct entry to Class II for operators with significant prior experience. Confirm the rule with your state certifying authority.
What size facility can a Class II operator run?
Class II typically authorizes operation of small-to-medium wastewater treatment facilities. Exact facility classification thresholds (population served, flow, treatment complexity) are set by each state authority and are not uniform across jurisdictions.
How should I study for Class II?
Focus first on activated sludge process control: SRT, F/M, SVI, RAS and WAS rates. Then biological nutrient removal, anaerobic and aerobic digestion, 503 biosolids handling, and safety. Approximately 14% of questions are calculation-based, so practice wastewater math and process control formulas.